1. Field of the Invention
This invention relates to a display apparatus comprising pixel cells arranged to form a matrix. More particularly, the present invention relates to an inspection method for detecting defects in the gate lines and the data lines for driving pixel cells of a display apparatus and also to a display apparatus adapted to such an inspection method.
2. Description of the Related Art
Liquid crystal display apparatus employing an active matrix system have been and being popularly used for liquid crystal projectors and liquid crystal displays.
A liquid crystal display apparatus employing an active matrix system typically comprises, if the apparatus is of the reflection type, pixel switches and pixel cells connected to the respective pixel switches and having respective pixel capacitances and the pixel cells are arranged on a semiconductor substrate to form a matrix. An opposed substrate carrying a common electrode is arranged vis-à-vis the semiconductor substrate and liquid crystal is put into the gap between the semiconductor substrate and the opposed substrate and held there as the gap is hermetically sealed.
In such a liquid crystal display apparatus, some of the gate lines for driving the pixel switches and the data lines for supplying pixel data to be written to the pixel capacitances by way of the respective pixel switches can be short-circuited by the shortcomings produced in the process of manufacturing the semiconductor substrate of the liquid crystal display apparatus and/or the dust coming into the apparatus. When such a problem of short-circuit arises, linear defects appear in the displayed image of the liquid crystal display apparatus.
Various techniques have been proposed to date for the purpose of detecting short-circuiting in the gate lines and the data lines that give rise to such linear defects.
For example, a technique of arranging pads at the ends of the data lines and the gate lines and applying a probe directly to the pads to detect short-circuiting (refer to patent Document 1: Japanese Patent Application Laid-Open Publication No. 2001-201765) and a technique of arranging short-circuit test circuits connected to the data lines and the gate lines respectively at the side of the drive circuit for driving the data lines and the gate lines and at the side separated from the former side by the display region (refer to patent Document 2: Japanese Patent Application Laid-Open Publication No. 10-97203) are known.
However, when a liquid crystal display apparatus is configured in such a way that it has a plurality of display regions produced by dividing the display region vertically or horizontally for the purpose of avoiding degradation of the quality of the displayed image due to the increase in the load of the data lines and the gate lines and the display regions produced by the division are driven independently, it is physically impossible to arrange pads or test circuits in a manner as described above.
Thus, there has been proposed a technique of connecting the data lines of each display region produced by dividing the overall display region by way of transistors and checking if there is a broken line or not by applying a voltage to an end of the data lines and observing the electric current flowing at the other end (refer to patent Document 3: Japanese Patent Application Laid-Open Publication No. 2001-188213).